All the parts are recycled materials. The base is a discarded fan base, 18" in diameter. The 15" diameter platform is a round piece of plywood from my scrap wood collection.
The pole in this feeding platform telescopes for height adjustment. It came from another fan base. When my cat was smaller, he needed a 5-gallon bucket set next to the platform as a step for getting up to the food. Not any more.
Step 1: THE BASE
The wood under the platform has a hole that fits over the top of the vertical stand pole, thus securely holding the platform.
The feed bowl is made to slide on and off the piece of wood that protrudes from the side of the platform. I used some PVC material from pipe scraps to make the channel underneath the bowl that holds it in place.
Step 2: THE PLATFORM
There is a piece of 3 X 4 wood with a hole drilled in it that is nailed to the bottom of the platform. The hole slides over the vertical base pole and holds the platform in place. It also allows the top of the platform to spin a little on the pole. There is enough friction that it doesn't spin when the cat jumps onto it.
If you make this design from store-bought materials, you could probably use a section of threaded metal pipe with flanges at top and bottom for mounting it to a plywood base and plywood platform.
As another alternative, you could probably get a piece of large-diameter PVC pipe with flanges for mounting the top and bottom to plywood in the same way.
Step 3: THE BOWL
I added on this PVC to the bowl I had by cutting a strip section from a piece of pipe, heating it over a gas stove and forcing it into shape over the bowl and piece of wood until it cooled.
You might find it simpler to get two nesting bowls. Screw one of them to the wood. The food bowl will rest in the holding bowl, and be easily removable for washing.